REFLECTOR: Fwd: My Velocity setup

[Alex Balic]

Ronnie-
I think Doug was thinking of making a sort of ducted fan on the prop shaft
at the round opening in the center- this seems like a good idea- certainly
would move some air if the blades were of any significant length. might help
out in ground cooling anyway.
  -----Original Message-----
  From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org]On
Behalf Of Ronnie Brown
  Sent: Friday, December 03, 2004 12:21 PM
  To: Velocity Aircraft Owners and Builders list
  Subject: Re: REFLECTOR: Fwd: My Velocity setup


  Hi Doug,

  Not to be a wise A_ _, but there already is a fan there, most of them are
three bladed.

  Kidding aside, there has to be a lot of vacuum at the cowl exit created by
the prop.  I have the top NACA inlets, and my engine runs nice and cool,
even on the ground on hot days.  I didn't have any problems at Oshkosh last
year, although it was not the worst Oshkosh kind of day when I landed and
lots of taxiing to get to "Area 51".  Take off was a non issue as it was low
over cast and nobody was leaving except me and Gilles

  Even on 90 degree days taxiing on medium runways has not been a problem -
no more than 350 degrees CHT.  My cowl is within 1" of the prop leading
edge, a number that Alan Shaw said was optimum for pulling air out of the
engine.  By the way, I have a temperature sensor mounted at the bottom of my
alternator - near the outlet of the cowl.  It hardly ever goes over 180, I
have seen it at 200 after a climb out on a hot day.

  Ronnie

  ----- Original Message -----
    From: Douglas Holub
    To: Velocity Aircraft Owners and Builders list
    Sent: Friday, December 03, 2004 12:19 PM
    Subject: Re: REFLECTOR: Fwd: My Velocity setup


    Would it help to suck air through the NACA ducts if I put a fan on the
prop extender just before it exits the cowl?

    Doug Holub
      ----- Original Message -----
      From: Al Gietzen
      To: 'Velocity Aircraft Owners and Builders list'
      Sent: Friday, December 03, 2004 10:54 AM
      Subject: RE: REFLECTOR: Fwd: My Velocity setup


      My idea behind this is to scavange some of the flow that comes through
the bottom radiator, across the bottom of the pan, and out the "suction
slot".  at about 18" from the center of prop rotation, it should also add to
the suction the prop places on the cowl opennings. Well.. at least that is
my idea, we'll see if it works out. I am hoping that I can get away without
an oil cooler with that setup. No worries though, I have a backup to put an
inline cooler on the #2 NACA scoop if I need it.



      Keep in mind that the reduced pressure (“suction”) generated by the
prop dissipates rapidly (exponentially) as you move away from the prop, so
even a foot is a long way - and at cruise it is almost non-existent; you
have to rely on dynamic pressure and whatever gradients are produced by the
flow.  Remember, the air is standing still, the airplane is moving.  Some
air is getting pushed/pulled downward by the airfoils, some is being pushed
back by the prop, the rest is getting out of the way as best it can.



      Al



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